CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating activities
Net loss	$ (7,293)	$ (4,403)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	31	27
Stock-based compensation	238	104
Non-cash interest expense	129	1,365
Change in fair value warrant liability		(5)
Change in fair value derivative liability		162
Changes in operating assets and liabilities:
Other receivable	(437)
Prepaid expenses and other assets	(99)	246
Accounts payable	225	129
Accrued expenses	(1,533)	(257)
Deferred rent	8	(2)
Net cash used in operating activities	(8,731)	(2,634)
Investing activities
Purchases of property and equipment	(84)	(6)
Net cash used in investing activities	(84)	(6)
Financing activities
Long-term borrowings, net	616
Repayments of long-term debt	(938)
Net cash used in financing activities	(322)
Net decrease in cash and cash equivalents	(9,137)	(2,640)
Cash, cash equivalents and restricted cash at the beginning of the period	61,051	13,406
Cash, cash equivalents and restricted cash at the end of the period	51,914	10,766
Supplemental disclosure for cash flow
Cash paid for interest	98	39
Supplemental disclosure of non-cash investing and financing activities
Accrued interest on term loan refinanced to principal	308
Issuance of warrants in conjunction with debt	209
Debt refinanced with new term loan	6,563
Initial recognition of operating lease right-of-use assets and operating lease liabilities	1,991
Accretion of redeemable convertible preferred stock		16
Purchases of property and equipment included in accounts payable	$ 11	$ 10